The use of whitening agents, either optical brighteners or blueing agents, in textile applications is well known in the prior art. As textile substrates age, their color tends to fade or yellow due to exposure to light, air, soil, and natural degradation of the fibers that comprise the substrates. Thus, the purpose of whitening agents is generally to visually brighten these textile substrates and counteract the fading and yellowing of the substrates. Typically, whitening agents may be found in laundry detergents, fabric softeners, or rinse aids and are therefore applied to textile substrates during the laundering process. However, it is important that whitening agents function to brighten treated textile substrates without causing undesirable staining of the textile substrates.
Cellulosic substrates, in particular, tend to exhibit a yellow hue after exposure to light, air, and/or soiling. This yellowness is often difficult to reverse by normal laundering procedures. As a result, there exists a need for improved whitening agents which are capable of eliminating the yellowness exhibited by ageing cellulosic substrates. By utilizing such improved whitening agents, the life of the textile substrates, such as clothing articles, table linens, etc., may be extended.
The present invention offers advantages over U.S. Pat. Nos. 4,137,243, 5,039,782 and US Patent Application Publication No. 2005/0288206 as this invention takes advantage of compounds having a Hansen Solubility Parameter of less than or equal to about 17 MPa0.5 and which emit light with wavelengths in the range of blue, red, violet, purple, or combinations thereof upon exposure to ultraviolet light (or, they absorb light to produce the same shades) in order to neutralize the yellowness of cellulosic substrates. These compounds function ideally as whitening agents for cellulosic substrates and may be incorporated into laundry detergent formulations for use by consumers during the laundering process.